Paraplegia is a serious complication thought to occur in 5-20% of surgery cases due to defective circulation of the spinal root arteries, the nutrient vessels of the spinal cord, at the time of surgery for thoracoabdominal aortic aneurysm. When the thoracic aorta is blocked at ordinary temperature, it is believed, irreversible damages of spinal nerves develop in about one hour (Svensson L G, Crawford E S, Hess K R, Coselli J S, Safi H J. Experience with 1509 patients undergoing thoracoabdominal aortic operations. J Vasc Surg 1993; 17:357-70). However, during operations, it is very difficult to specify the spinal root arteries from a multitude of intercostal arteries, and its reconstruction often takes a lot of time.
Clinical tests and studies have already demonstrated that maintaining a low body temperature by central cooling with an artificial heart and lung during operations is useful for spinal cord protection (Kouchoukos N T, Wareing T H, Izumoto H, et al., Elective hypothermic cardiopulmonary bypass and circulatory arrest for spinal protection during operations on the thoracoabdominal aorta. J. Thorac Cardiovasc Surg 1990, 99:659-64). However, systemic hypothermia may disadvantageously induce demerits such as abnormal coagulation and respiratory disorders due to extracorporeal circulation. At present, there are no methods that can completely avoid the occurrence of paraplegia associated with surgery for the thoracoabdominal aortic aneurysm.
As methods of topical cooling of the spinal cord, there have been reported a method in which two catheters are separately inserted to the subarachnoid cavity (the spinal cord cavity) (one for injection that injects cooling water, and the other for discharging for use in the drainage of the cooling water) and topical cooling is accomplished under perfusion of the spinal cord (Paul A., Spinal cord protection during thoracoabdominal aneurysm resection. J. Thorac Cardiovasc Surg 1995, 109:1244-6). With this method, however, when the drainage of the cooling water becomes poor, internal pressure of the subarachnoid cavity may be excessively enhanced which may cause serious complications such as cerebral hernia, and thus its clinical application was difficult. Furthermore, Cambria of Harvard Univ. has reported a method in which a catheter was transdermally inserted in the surgery of thoracoabdominal aortic aneurysm, through which a cooling water was continuously injected, and during one operation about 1400 ml of physiological saline was injected without drainage and allowed to diffuse as it is without drainage (Cambria R P, Davidson J K, Zannetti S et al., Clinical experience with epidural cooling for spinal cord protection during thoracic and thoracoabdominal aneurysm repair. J. Vasc Surg 1997, 25:234-43; Cambria R P, Davidson J K. Regional Hypothermia for Prevention of Spinal Cord Ischemia complications after thoracoabdominal aortic surgery: Experience with epidural cooling. Seminars in Thoracic and Cardiovascular Surgery, Vol. 10, No. 1 (January), 1998, pp. 61-65). With this method, however, due to the cooling water injected, internal pressure of the subarachnoid cavity may be excessively enhanced leading to about twice the normal internal pressure of the medullary cavity, and thus because of potential risk of ischemic disorders such as cerebral hernia and reduced perfusion pressure, the method has not been adopted in other facilities. Furthermore, experimentally, although there has been reported a method of injecting a bolus of cooling saline into the subdural cavity, the method does not permit the continuous cooling of the spinal cord for a long time. These two methods have been developed for the cooling of the spinal cord in the operation room, it is necessary to inject the cooling water into the epidural cavity while monitoring internal pressure of the subarachnoid cavity and intraspinal temperature so that internal pressure of the subarachnoid cavity may not be excessively enhanced. Thus, since the methods are troublesome in management, and the amount induced into the epidural cavity is limited, it is not amenable to continuous cooling for a long time in intensive care units or general hospital wards.
On the other hand, traumatic brain contusion is caused by traffic accidents or accidents, and significantly affects the mortality and morbidity of those involved, posing a serious social problem as well. The general hypothermic therapy for traumatic brain contusion has a concept that nerve cells that were damaged, specifically those cells that received medium irreversible damages, which may be considered to be a penumbra retaining a potential of recovery, present in the periphery of nerve cells that received irreversible damages are protected by a nerve cells-protecting effect retained by hypothermia so as to improve the prognosis and QOL of the patient. Its usefulness has already been recognized and has been put into clinical practices such as in the form of surface-cooling the entire body with a blanket at a medium body temperature of about 32° C. (Jiang J., yu M., Zhu C., Effect of long-term mild hypothermia therapy in patients with severe traumatic brain injury: 1-year follow-up review of 87 cases. J. Neurosurge. 2000, 93(4):546-9). However, there are demerits such as decreased immune functions associated with maintaining the hypothermia of the entire body, and the resulting infections, arrhythmia or abnormal coagulation. In particular, it has been pointed out, when the patient is an elderly, demerits such as infections associated with the hypothermia of the entire body becomes pronounced leading to the onset of complications, with a result that the overall survival is not improved. Also in order to overcome the demerits such as infections, arrhythmia and abnormal coagulation, complicated management of the entire body at the intensive care unit is required causing economic problems that more labor and cost are required. Specifically, when the treatment is prolonged, the brain hypothermia therapy that maintains the hypothermia of the entire body requires an enormous personnel and economic costs.
Also, there is a need for the development of devices for topical cooling the esophagus as a means of preventing esophageal injuries that may occur as a complication at the time of radiofrequency ablation for the atrium performed as a method of treatment of atrial fibrillation.